Matthew Fero is a medical oncologist with research interests which focus on the role of cell cycle genes the development of cancer and in the control of cell growth. This award permits Dr. Fero to further our understanding of tumor suppression by the cell cycle inhibitor (CKI) gene p27kip1, while making a transition in his career from the position of a mentored researcher to an independent investigator. The proposed studies utilize the skills Dr. Fero has acquired in the manipulation of the mouse embryo to produce mutations in laboratory mice which are specific both to genes of interest and confined to particular tissues. These novel gene mutations will then be combined with well defined murine models of induced carcinogenesis and gene expression analysis to define the mechanism of tumor suppression of p27 and it's biochemical effects in tumorigenesis. By developing mice which harbor cell cycle gene mutations confined to the pituitary or thymus it will be determined whether the p27kipI can induce adenomas and lymphomas in these tissues in an autonomous fashion, that is independent of the influence of factors from surrounding cells or tissues. Likewise analysis of intestinal tumors, lymphomas and prostate tumors developing in mice which are genetic mosaics for p27 gene mutations will determine whether these tumors also arise in an autonomous fashion. The mechanism of tumor suppression by p27 will be further defined in each model system and the patterns of altered gene expression and cell cycle protein function will be characterized. If p27 mutations cause tumors in a cell non-autonomous fashion it will be important to determine the signaling pathway which acts between the p27 deficient cell and the neoplastic cell. Therapeutic agents may then be targeted at either the cell cycle proteins or the intracellular molecules which mediate cancer development.